The risk of malfunctions in medical equipment due to electromagnetic interference (“EMI”) from mobile RF sources has been a long-standing problem. One problematic RF energy source is mobile phones that may be carried by hospital workers, patients and visitors and which are used more pervasively throughout hospitals as time progresses. Another problematic RF energy source is mobile data devices. Hospitals have begun to embrace wireless networking technology such as IEEE 802.11 WLANs to increase productivity, including clinical productivity, requiring the use of wireless equipment in proximity to clinical equipment. For example, some health care workers now use wireless-connected PDAs and laptops to retrieve, review, enter, display and coordinate data regarding patients. Such data might include images such as x-rays, MRIs and CT scans, in addition to medication schedules, and medical history. Within buildings it is possible that mobile phones will soon be using WLANs for communication. Hence, it is not practical to simply prohibit the problematic devices from the hospital.
Passive shielding against electromagnetic interference (“EMI”) has been used in the field of electronics for a considerable time. A signal line, component, or circuit board that will be subjected to unacceptable levels of EMI is shielded by partially or completely surrounding it with a grounded conductor. Such passive shielding is typically used to protect against EMI from within a device, or from adjacent devices. However, much of the medical equipment currently in use was not designed to shield against close proximity with WLAN devices and mobile phones. Further, retrofitting medical equipment with passive shielding would be costly and time-consuming.